SU915683A1 - Optical radiation converter - Google Patents

Abstract

A device for converting electromagnetic radiation into an electrical signal comprises two interconnected semiconductor layers (1 and 3) with bandgaps (2 and 4) differing in width. The semiconductor layer (1) having the wider bandgap (2) is made of a material whose structure permits providing an inhibit contact for charge carriers of both signs. The structure of the material of this layer additionally permits forming trapping sites for the charge carriers. Electrodes (9 and 10) with fermic levels 19, 20 are, respectively, arranged on the side of free surfaces of the semiconductor layers (1 and 3). Other embodiments include a dielectric layer in addition to the layers 1, 3. <IMAGE>

Description

The invention relates to the field of semiconductor devices that register optical signals and images and can be used in optoelectronics. '

Known converters of electromagnetic radiation into an electrical signal based on heterojunctions — £ 1-2-. -.....

These transducers do not allow to record optical images.

• The closest technical solution is an optical signal converter into an electrical signal based on a structure containing two semiconductor layers with different widths of C22 band gap.

A translucent metallic layer is applied to the surface of the wide-gap semiconductor of this converter. When the detected radiation hits the converter, the optical image is transformed into a potential relief created in the layer of a wide-gap semiconductor due to recharging its capture centers with photocarriers.

The disadvantages of this device include the technological difficulties that arise when applying a thin 1 μm) · wide-gap layer, which must be continuous. The lack of continuity in the wide-gap layer leads to the shorting of the metal electrode on the narrow-gap substrate, which does not allow reading the recorded information, since the video signal in this case is completely shunted.

Ultimately, this will reduce the percentage of yield of devices. In addition, the efficiency of hitting photo carriers on the capture centers of the wide-gap layer and, consequently, the sensitivity of such a converter is limited due to the fact that a significant part of the carriers are excited, leaves light in the zones of the allowed energies of the wide-gap layer and does not hit the capture centers.

The aim of the invention is to increase the sensitivity while increasing the percentage of yield of devices.

This goal is achieved by the fact that in the proposed converter of electromagnetic radiation into an electrical signal based on a structure containing two semiconductor layers with different widths of the forbidden zones, at least one of the sides of the wide-gap semiconductor layer, there is a dielectric layer 5010000 A thick, whose resistance is not less 10 ⁷ ohms in the direction perpendicular to the structure plane. The dielectric layers, creating a barrier for carriers that fall into the zones of the allowed energies of the wide-gap layer, impede the release of carriers from the wide-gap layer, thereby increasing the probability of their capture, which leads to an increase in the sensitivity of the device. In addition, the presence of the dielectric layer compensates for the absence of continuity in the layer of the wide-gap semiconductor and thereby increases the percentage of output of workable devices.

Figure 1-3 shows the band diagrams of the three types of the proposed Converter. *

The converter contains a semitransparent metal with the following 1, a wide-gap semiconductor layer 2, a dielectric layer 3 and a narrow-gap semiconductor layer 4.

. In the case shown in figure 1, the dielectric layer 3 is located between the layers of narrow-gap 4 and wide-gap 2 semiconductor. Under the action of the detected radiation, photoemission of electrons from the metal Γ to the wide-gap semiconductor 2 occurs, where they are effectively captured at the trapping centers, since dielectric layer 3 prevents them from entering the narrow-gap semiconductor 4. This case is realized on structures such as 3ί35.0 ^ metal, Ge-Zto-CpZe-metal. For these structures, the long-wave boundary for recording optical information is determined by the value of potential barriers for current carriers at the metal .η5ε interface and is раздела 1.2 μm.

Figure 2 shows the case where the dielectric layer 3 is located between the metal layer 1 and the wide-gap semiconductor layer 2. In

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In this case, photoemission of electrons from the narrow-gap semiconductor 4 to wide-gap 2 is used to recharge capture centers. This case is realized in the Lp3 system anodic oxide - 3–0 - metal. For her, the long-wavelength limit for the 'record lies near 1 μm.

The above-described variants of the converter work in the same way in the case of using hole photoemission (from metal 1 in the first case and from narrow-gap semiconductor 4 in the second case) to recharge the corresponding capture centers of the wide-gap semiconductor 2.

Fig. 3 corresponds to the case when two dielectric layers 3 are located on both sides of the wide-gap semiconductor 2. The recorded radiation causes the formation of electron-hole pairs in the layer of the wide-gap semiconductor 2, where they are separated in an external field and captured at the corresponding centers. The presence of two dielectric layers with such a recording mechanism is necessary to create potential barriers for carriers of both signs and thus to increase the recording efficiency. As an example, the structure of the 3ίЗхО ^ -ЕПЗе-ЗхО-metal can be given. The long-wavelength boundary is determined by the recording by the width of the forbidden zone Ζη3β and is about 0.47 μm.

For all the cases presented, the thickness of the dielectric layer 3, located between narrow-gap 4 and wide-gap 2 semiconductors, should be as small as possible (but tunnel-opaque for current carriers, that is, at least 50 Hu,

which makes it possible to more effectively convert a potential relief 6 into an electrical signal, for example, by scanning the structure with a light beam. On the other hand, the dielectric layer 3 must be sufficiently uniform in thickness and electrically strong. On this basis, limits are established for the thickness of the dielectric layer 3 50-10000 X.

. The specific resistivity magnitude 'for the specified thickness limits is in the range 10 ¹ ^ - 10 ²² 0m / cm, while ensuring the value of series resistance ,; structure of at least ^7, ~ U 0m that excludes video bypass when the recorded information is read.

The potential relief can be erased using thermally stimulated emptying of the trapping centers or recharging them with the currents of the intrinsic photoconductivity of the wide-gap semiconductor at different polarities of the voltage on the structure. In addition, in the first and second cases, for erasing, the emission of a wide-gap semiconductor of current carriers of opposite sign from the metal layer or from the narrow-gap semiconductor layer can be used during the polarization of the voltage source connected to the structure. In ve ustroyst ³⁵ based δΐ-δΐΟ ^ -Ζηδε sensitivity was obtained to the recording radiation to Yu ^'9 J / cm ^z at the exit area of structures I cm ² of more than 80%. Whereas famous

⁴ θ structures 5ϊ-Ζη8ε have sensitivity up to 1O ' ⁱⁿ yes / cm' ² with the output of workable structures not more than 10%.

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Claims (2)

OPTICAL RADIATION CONVERTER to an electrical signal based on a structure containing two semiconductor layers with different band gap widths, characterized in that a dielectric layer is placed to increase its sensitivity while simultaneously increasing the yield percentage on at least one side of the wide-gap semiconductor layer thickness 50-10000 k, the resistance of which is not less than 10 ⁷ ohms in the direction perpendicular to the plane of the structure. _about <e with Sl 05 00 with 1 > one 915683 2